As a device for transmitting and displaying an image with optical fibers, two types are generally known. One is the so-called image guide or imagescope which displays a full-size image with optical fibers densely bundled in the same arrangement for both incident and image display planes, and the other is an image display device having a function enlargement with a greater clearance of optical fibers provided for the image display plane than for the incident plane to form a large screen of an image size of several feet. In either case, the image display surface (screen surface) is formed by cut end faces of the optical fibers. However, the beams of light coming from the end faces are highly directional, and so the image may be clearly seen in a certain range of angle to the image display surface, that is, in a nearly vertical direction. However, it becomes very difficult to observe the image as that angle to the perpendicular of the image display surface increases. That is, such a device has a shortcoming that the angle of the field of vision is limited. Then, in the case of a large size screen which is particularly intended for a number of persons to see at the same time, some means are required to scatter the outcoming light over a wide range of angles.
The conventional countermeasures to this problem are classified largely into two methods: one is to scatter the light emitted from the optical fibers with a light scattering plate or film pasted on the image display surface (which will be referred to as "screen surface" in the following where a large screen is concerned); and the other to provide a light scattering structure at the end face of optical fiber. According to the former method, the light scattering plate or film reflects the environmental disturbing light, and hence has the disadvantage that the reflected light comingles with the image information displayed thus obscuring the image or, more specifically, reducing the resolution and contrast of the image. As for the latter method of providing a light scattering structure at the portion from which light is emitted, it is practically impossible to work up the end face of each of an optical fiber bundles, especially for a large screen having a hundred thousand of optical fibers present on the screen surface.
There has also been proposed a method of laminating the optical fibers in parallel in a tilted condition at a certain angle to the screen surface, that is, forming the screen surface with the end faces of the optical fibers cut at less than a perpendicular angle to the axis of the optical fiber (Patent Publication No. SHO 61-11782). According to this method, however, the rate of enlargement to the plane of incidence and the scattering on the screen surface or the field angle are simultaneously determined by the extent of tilting in the axial direction of the optical fiber bundles. Thus, it is impossible to independently and separately adjust both elements.
In view of the foregoing shortcomings in the prior art, it is the object of the present invention to provide, by a very simple method, a display device which has a wide angle of the field of vision and which is capable of producing a highly resolved, clear image where the image information is easily recognized.